This invention relates generally to fine needle aspiration (FNA), biopsy devices, and in particular to control systems for automatically controlling the operation of an FNA biopsy device so as to carry out a biopsy procedure.
A biopsy procedure involves the extraction of a small sample of living tissue from an internal mass in a patient, the extracted sample being then examined under a microscope in order to diagnose the patient""s condition. Where and how a biopsy is to be performed depends on the internal site of the suspected mass. A biopsy is usually called for when other diagnostic techniques are unable to supply sufficient information on which to base a diagnosis. Thus a physician can by means of an ultrasound imaging instrument locate and observe an internal tumor in the body of a patient. But an ultrasound image of this tumor does not indicate whether it is benign or malignant. A biopsy is therefore necessary to make this determination.
A biopsy can be conducted either by an open or by a percutaneous method. An open biopsy entails an invasive surgical procedure to expose the internal region of interest so that one can then excise a portion of the suspected mass and examine it under a microscope. In a percutaneous biopsy, a large bore needle is used, making it necessary to make an incision in order to obtain a tissue sample from a suspected mass. A large bore needle carries with it the risk of tumor seeding along the biopsy tract.
The present invention deals with the least disturbing of biopsy techniques; namely: xe2x80x9cFine Needle Aspirationxe2x80x9d (FNA). In an FNA technique, a fine needle projecting from a syringe is injected into a patient to impinge on an internal target from which the needle extracts a tissue sample constituted by a cluster of cells. The small sample picked up by the needle is then sucked into the syringe for cytologic examination under a microscope.
In an FNA biopsy procedure, it is vital that the injected needle be accurately directed to strike the target of interest and avoid adjacent tissues. When the target is palpable, such as a bulging thyroid gland, a physician has no difficulty in directing the needle toward the target. In this situation, all that a physician need do is to grasp in one hand the bulging tissue mass and with his other hand to inject the needle of the FNA device into the mass to extract a sample therefrom. The syringe is then operated to suck the sample from the needle into the syringe from which the sample is later removed for examination To facilitate such manual operations, various devices have been devised to hold the biopsy syringe. One such device for this purpose is disclosed in U.S. Pat. No. 5,493,130.
In those situations where the target for an FNA biopsy is not palpable but is deeply embedded in a patient""s body, such as in the liver, then in order to be able to guide the needle toward the internal target one must be assisted by an imaging instrument, making it possible for the physician to see the internal target and the position of the fine needle relative thereto. The imaging instrument used for this purpose may be an ultrasound instrument or a computer-assisted tomograph (CAT or CT).
In the medical field, the reason ultrasound imaging is a preferred diagnostic tool is because of the non-ionizing character of ultrasound radiation. This makes ultrasound imaging safe and innocuous so that a patient may be repeatedly subjected in an ultrasound examination.
Sounds generated in an ultrasound instrument lie within a 1 to 10 mHz frequency range. These sounds are produced by a piezoelectric transducer caused to vibrate by an electronic pulse generator. When placed at a site overlying an internal target of interest, the piezoelectric transducer emits sonic pulses which are propagated through the body of the patient and reflected by interfaces between tissues having different acoustic impedances, thereby producing echo pulses which are received by the transducer. Signals from the transducer are applied to the cathode ray tube (CRT) of a monitor associated with the transducer on whose screen is displayed an image of the internal target of interest and the tissue to surrounding the target.
In order for an ultrasound instrument to accurately lead the needle of an FNA biopsy device toward an internal target when tissues are suspect and require diagnosis, it is known to provide the transducer of the instrument with a needle guide, such as the needle guide disclosed in the U.S. Pat. No. 5,924,992 to Park et al. This needle guide makes it possible for a physician to see on the CRT screen of the monitor associated with the transducer an image of the target of interest and of the biopsy needle as it advances toward this target. Also of prior art interest in regard to the use of an ultrasound instrument to perform real-time image-guided biopsy of tissue is U.S. Pat, 6,027,457 to Shmulewitz et al.
A biopsy needle guide for use with an ultrasonic probe in a medical procedure to accurately position a biopsy needle with respect to an internal target is also disclosed in U.S. Pat. 5,494,039 to Onik et al.
A needle inserting guide associated with an ultrasound probe makes it possible for a physician to properly direct the needle toward an internal target. But the guide does not relieve the physician of the need to manually operate the biopsy device so as to advance the needle toward the target to extract therefrom a tissue sample, to then withdraw the sample from the target, and finally to transfer the sample from the needle to the syringe.
Moreover, while the needle insertion guide simplifies the spatial relationship of the needle, the ultrasound probe and the internal target being biopsied it is an impediment to navigation and to a clear three-dimensional display of the tissues. One can therefore understand why investigators have reported that the sensitivity of a free-hand biopsy is greater than the sensitivity of a needle guide technique (seexe2x80x94Hatadet et al. Tumor 1999; 85;12).
Existing biopsy procedures present difficulties to a physician, for he must while viewing the CRT screen of an ultrasound imaging instrument at the same time be holding the transducer of this instrument against the body of the patient, and as he holds this transducer with one hand, he must with his other hand manipulate the FNA device first to inject the needle into the patient to obtain a sample, second to withdraw the needle, and third to operate the syringe to transfer the sample thereto.
A logical form of automatic control system for an FNA biopsy device would be a system in which electrically-powered miniature motors act to advance and retract the fine needle to extract a tissue sample from an internal target, and to then manipulate the syringe to transfer the sample from the needle to the syringe.
Of prior art interest in regard to a motor-driven automated biopsy device is the U.S. Pat. 5,980,469 to Burbank et al. However, conventional electrically-powered motors in a control system associated with a biopsy device in proximity to an ultrasound transducer through which the needle is guided cannot be tolerated. The reason for this is that relatively strong magnetic fields emanating from the motors and enveloping the transducer may interfere with its operation and distort the images appearing in the CRT screen. Moreover, a conventional motorized control system for a biopsy device which must be held by a physician in the course of a biopsy procedure enlarges the bulk and weight of the device and therefore makes it more difficult to handle.
Another drawback of a motor driven biopsy device is that it is difficult with a conventional motor to advance or retract the needle to the precise degree required by a biopsy procedure.
In our pending Israel Patent 140,494 filed Dec. 22, 2000, there is disclosed a pneumatic control system for automatically controlling the operation of an FNA biopsy device to be injected into a patient to extract a tissue sample from an internal target to be transferred to the syringe.
The control system includes a cylinder having a piston slideable therein to which the FNA device is coupled, movement of the piston advancing or retracting the needle. In an operating cycle, a computer-controlled pneumatic supply feeds air at positive pressure into the cylinder in a region above the piston to cause the piston to advance the needle toward the target to extract a tissue sample therefrom, and to then feed air at positive pressure into the cylinder in a region below the piston to cause the needle to retract and withdraw the sample. For the final phase of the operating cycle, air at negative pressure is fed into the syringe, causing the sample to be sucked from the needle into the syringe.
The pneumatic control system disclosed in our pending application acts by means of positive and negative air pressures to fully automate the operation of an FNA biopsy device. But it does not create electromagnetic fields that may disrupt the operation of the ultrasound transducer with which the biopsy device is associated. Of prior art interest in his regard is the automatic control system for a vacuum-assisted core biopsy device disclosed in U.S. Pat. 6,017,316 to Ritchart et al. In the system shown in this patent it is only negative pressures creating a vacuum that is used throughout the control system.
In a biopsy procedure the degree of accuracy required depends on the nature of the target from which a tissue sample is to be extracted. In many situations, all that is necessary is a reasonable degree of accuracy rather than a high degree of precision. However, in some situations, greater precision is desirable.
Thus in a lung biopsy, the needle must make contact with the surface layer of the lung to extract a tissue sample therefrom. But the operator must exercise care to avoid penetrating the lung and causing it to collapse. Yet because it is difficult to precisely position the needle, in a fair percentage of lung biopsy procedures, lung collapse is experienced.
In view of the foregoing, tile main object of this invention is to provide control systems for automatically controlling the operation of an FNA biopsy device by a pneumatically operated or a motor driven mechanism.
A significant feature of an automatic control system in accordance with the invention is that it relieves a physician conducting an FNA biopsy of the need to manually inject the needle into the patient in order to extract a tissue sample from an internal target and then operate the syringe to transfer the sample thereto from the needle.
More particularly, an object of this invention is to provide an automatically-controlled FNA biopsy device associated with an ultrasound imaging instrument whose transducer has a passage extending therethrough to guide the needle of the device into the body of a patient.
This passage in the transducer or ultrasound probe is through the dead center thereof, as a consequence of which the sensitivity of a free-hand biopsy device is enhanced.
Yet another object of the invention is to provide a control system in which the needle of the FNA biopsy device is advanced by a stepping motor energized by DC pulses whose repetition rate determines the rate at which the needle is advanced toward a final position.
Also an object of this invention is to provide a control system for an FNA biopsy device whose operation is governed by a computer programmed to accommodate the biopsy procedure to the requirements of the patient being treated.
Briefly stated, the objects are attained in a control system for governing the operation of an FNA biopsy device, provided with a syringe and a fine needle projecting therefrom to be injected into a patient to extract from an internal target a tissue sample which is then transferred to the syringe. Associated with the FNA device is an ultrasound imaging instrument having a transducer placed on a body site overlying the internal target and coupled to a CRT monitor. The needle is injected into the patient through a guide passage in the transducer. Hence displayed on the CRT screen is an image of the internal target and that of the advancing needle.
The FNA biopsy device is controlled by a pneumatically-operated or motor-driven mechanism linked to the guide tube through which the needle extends. In a first phase of an operating cycle, the mechanism causes the needle to advance toward the target to extract a tissue sample therefrom. In a second phase, the mechanism acts to retract the needle and withdraw the sample. And in a final phase, the syringe is manipulated to transfer the tissue sample from the needle to the syringe.